On 2018-04-14 23:14, Guido van Rossum wrote:
That actually sounds like a pretty big problem. I'm sure there is lots
of code that doesn't *just* duck-type nor calls inspect but uses
isinstance() to decide how to extract the desired information.
In the CPython standard library, the *only* fixes that are needed
because of this are in:
- inspect (obviously)
- doctest (to figure out the __module__ of an arbitrary object)
- multiprocessing.reduction (something to do with pickling)
- xml.etree.ElementTree (to determine whether a certain method was
overridden)
- GDB support
I've been told that there might also be a problem with
Random._randbelow, even though it doesn't cause test failures.
The fact that there is so little breakage in the standard library makes
me confident that the problem is not so bad. And in the cases where it
does break, it's usually pretty easy to fix.
Finally: changing the classes of certain objects is exactly the point of
this PEP, so it's impossible to achieve 100% backwards compatibility.
Jeroen.
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